1. Technical Field
The present invention relates to a printing technique which uses pigment ink and dye ink.
2. Related Art
One known example of a printing device is an inkjet printing device which forms a printed image by discharging ink from nozzles onto a print medium to form ink dots (Japanese Laid-Open Patent Application Publication No. 11-188896, for example). Among inkjet printing devices, there are those which perform printing using two types of ink: pigment ink and dye ink. The term “pigment ink” refers to ink that uses a pigment as the ink coloring, and the term “dye ink” refers to ink that uses dye as the ink coloring. In comparison with dye ink, pigment ink commonly does not run readily on print paper and has low transparency, and pigment ink is therefore suitable for printing letters and other solid images. In comparison with pigment ink, dye ink runs readily on print paper and has high transparency, and dye ink is therefore suitable for printing photograph images.
When both pigment ink and dye ink are used to form a printed image, it is known that there are cases in which the colors expressed have different concentrations, depending on the order in which the ink dots of pigment ink and the ink dots of dye ink overlap. In a printing device which moves a print head back and forth to perform two-way printing, when the pigment ink nozzles and the dye ink nozzles are arranged in parallel in the movement direction of the print head, there is a switching of the order in which the pigment ink and the dye ink are discharged between the advancing and retreating of the print head. Therefore, with such a printing device, tone properties differ between printed images formed during the advancing of the print head and printed images formed during the retreating, and there is a possibility that the quality of the printed image will decrease.